Members of the genus Chlamydia are obligate intracellular parasitic bacteria which the etiologic agents of various human diseases including non-gonococcal urethritis, conjunctivitis, and pneumonia. They are believed to owe their obligate intracellular mode of reproduction to a requirement for energy intermediates such as ATP and other nucleoside triphosphates. The basic objective of the proposed research is to establish conditions which permit host-free C. psittaci and C. trachomatis organisms to efficiently synthesize DNA, RNA, and protein. The specific aims are: 1) determination of the steady-state levels of adenine nucleotides and identification of enzymes involved in nucleotide synthesis, interconversion, and degradation in host-free chlamydiae; 2) characterization of mechanisms of transport of selected nucleotides by chlamydiae; 3) detection and characterization of nucleic acid synthesized in host-free chlamydiae; 4) characterization of the mechanisms of transport of selected amino acids; 5) detection and characterization of proteins synthesized by host-free chlamydiae; 6) conversion of the metabolically inactive form of C. psittaci (the elementary body) to the metabolically active form (the reticulate body) in a host-free system or in lysates of host cells. Preliminary results indicate that host-free reticulate bodies of C. psittaci possess specific mechanisms for the transport of ATP, GTP, and lysine, and are capable of synthesizing RNA and protein (albeit at rates considerably lower than intracellularly dividing organisms). It is hoped that this research will provide a host-free model which will facilitate studies on the basis biology of chlamydiae, lead to alternative methods of diagnosis of chlamydial infections, and provide an efficient method for obtaining radioactively labeled chlamydial antigens. A long-range goal for this research is to achieve host-free growth of chlamydiae.